Washington, June 14 : Iraqi Prime Minister Nouri al-Maliki has publicly rejected key US terms for an ongoing military presence and anti-American Shiite cleric Moqtada al-Sadr called for a new militia offensive against American forces, which will be a major setback for President George W Bush's Iraq policy.

During a visit to Jordan, Maliki said negotiations over initial US proposals for bilateral political and military agreements had "reached a dead end."

He said talks would continue, but his comments fuelled doubts that the pacts could be reached this year, before the December 31 expiration of a United Nations mandate sanctioning the US role in Iraq.

Maliki indicated that the proposed compromise on immunity for contractors was insufficient. "We could not give amnesty to a soldier carrying arms on our ground," he said.

Maliki also raised an issue that is of deep concern to Congress, saying that Baghdad expected a firm US commitment to protect Iraq from foreign aggression.

Although that promise was made in an outline of the strategic framework signed by Maliki and Bush in November, the administration has since assured US lawmakers that it is a "non binding" agreement that does not require congressional ratification.

In addition to ending the UN mandate, Maliki said, "what we wish is . . . that if Iraq is subject to a foreign aggression it would be defended. And on the American side that was abandoned as well. So we reached a clear point of disagreement."

The moves by two of Iraq's most powerful Shiite leaders underscore how the presence of US troops has become a central issue for Iraqi politicians as they position themselves for provincial elections later this year.

Iraqis across the political spectrum have grown intolerant of the US presence, but the dominant Shiite parties -- including Maliki's Dawa party -- are especially fearful of an electoral challenge from new, grass-roots groups, The Washington Post reported.

As the controversy over US troops grew in the region, Foreign Minister Hoshyar Zebari scheduled the first high-level Iraqi Government contacts with the two US presidential contenders.

Zebari will meet privately on Sunday with Republican John McCain and hold a telephone conference on Monday with Democrat Barack Obama.

Maliki's comments came as Sadr called for a new-armed wing of his Mahdi Army militia to fight US troops. Sadr had ordered the militia to cease carrying weapons last August.

Sadr aides, some of whom appeared surprised by the cleric's announcement, said he wanted to issue the order now to avoid seeming as if he was responding to a US-Iraqi agreement if one is reached by the July deadline.